There is a receptor for the third component of complement (C3) in the human renal glomerulus. Scanning electron microscopic studies demonstrated that this receptor is on an epithelial cell. The presence or absence of this receptor was investigated in a series of patients in whom glomerular C3 was present to a variable extent. In those renal biopsies in which large amounts of C3 were deposited in vivo in the glomeruli, the C3 receptor was not detectable or only minimally detectable, whereas in those patients in whom only small amounts of C3 were deposited in the glomeruli, the C3 receptor was present. In the course of the studies another receptor for the Fc portion of immunoglobulin (Ig) was detected in the interstitial areas of the renal cortex. These receptors are detected by using sheep red blood cells (SRBC) coated with IgG antibody. BIBLIOGRAPHIC REFERENCES: Gelfand, M.C., Shin, M.L., Nagle, R.G., Green, I., and Frank, M.M. The glomerular complement receptor in immunologically mediated renal glomerular injuries. N. Eng. J. of Med. 295: 10, 1976. Shin, M., Gelfand, M.C., Nagle, R., Carbo, J., Green, I., and Frank, M.M. Localization of Receptors for Activated Complement on Visceral Epithelial Cells of the Human Renal Glomerulus. J. Immunol. 118: 869, 1977.